Fire alarm system



July 4, 1939. F. R. BRIDGES :1- AL FIRE ALARM SYSTEM Filed July 3, 19362 Sheets-Sheet 1 27 Eric I I, if?

TO'I'LIRE Jul} 4, 1939.

F; R. BRIDGES El AL 2,165,174

FIRE ALARM SYSTEM Filed July 3. 193's 2 Sheets-Sheet 2 F-L; $15 B '14 Aa I 13 h 4 i-LINE W $43 1 flf J Patented July 4, 1939 PATENT OFFICE FIREALARM SYSTEM Frank R, Bridges, Needham, and Foster E. Weld,

Newton, Mass., assignors to The Gamewcll Company, Newton Upper Falls,Masa. a corporation of Massachusetts Application July a, rose, serialNo. aa,ao1

6 Claims.

The present invention relates to die alarm systems.

Our copending application filed of even date herewith describes a firealarm system which is particularly adapted for small town use,principally because of the provision for substantially completeautomatic supervision. The central oilice equipment is arranged to becompletely housed in a small cabinet which is not necessarily kept underconstant personal attention.

The present invention contemplates, as an addition to the system, theprovision of built-=in testing equipment whereby the conditions existingin the line and central oflice circuits may be readily determined. Inthe preferred form of the invention, all of the test operations areeffected by a single manual switch by which an ammeter and a voltmetermay be variously connected into the circuits for indicating such factorsas line current and voltage, charging current and voltage, and thecondition of the line with respect to ground. An important feature isthat no setting of the test equipment can in. any way affect orinterfere with a signal in process of transmission or one which may besubsequently transmitted.

In the accompanying drawings illustrating what is now considered thepreferred form of the invention, Fig. 1 is a diagram of so much of thesystem as is necessary for an understanding of the invention, the switchgroups being shown in norm'al position; Fig. 2 is a view of the switchand meter panel; and Fig. 3 is a view of a portion of the system showingcertain of the switch groups in a different position from Fig. 1.

The illustrated embodiment of the invention comprises a single circuitsystem which is fully described in detail in our copending applicationabove referred to. The system includes a battery ill, the positiveterminal of which is connected by a wire II with. the positive side ofthe line. The negative side of the battery is connected to the negativeside of the line through connections to be hereinafter described. Theline connections include suitable operating .and signaling equipmentillustrated as a main relay M, a gong and a supervisory relays, theoperation of which is described in the copending application.

The cabinet within which the central oiiice equipment is contained has apanel provided -with a milliammeter l2, a voltmeter l3 and a test switchII. The test switch is a seven-position switch having a panel indicatingthe pos-. sible positions of the manual switch handle. The

switch includes eight contact groups indicated A to H inclusive in Fig.1, each group having a. set of contacts designated I, 2, 3 etc. Thecontact designated at i for each group is. a loop member which is actedupon by a cam operated 5 from the switch handle. The cams areillustrated diagrammatically at H in Fig. 1, each disposed adjacent tothe corresponding switch group. In a subsequent description the term"ca-mming refers to the action of a high point of a cam on the loopcontact of the corresponding switch group; thus in Fig. 1 group A onlyis ca'mmed and in Fig. 3 none of the groups are cammed.

The connections between the negative side of the battery and thenegative side of the line include a wire l5 connected between thebattery and contact 3 of group B. A wire i6 connects the contacts 2 ofgroups A and B. A wire [8 connects contacts I of both groups and thesame wire continues to contacts of the grounding or conditioning relayMG, which as described in our copending application is normallyinactive, but is arranged to condition the line for ground signalingwhenever the line is accidentally broken. So far as the presentinvention is concerned, only the contacts designated 28 to 24 inclusiveare important. The wire l8 connects with contacts 2| and 22, the contact2| being normally closed on 20 which is connected with the nega- 30 tiveside of the line. The contact 22 is associated with a contact 23 whichis connected to ground. The operation of the relay is fully disclosed inour copending application, and it will sumce to note here that upon itsenergization, the negative side of the line is disconnected from thebattery and is connected with the positive side of the line, while thenegative side of the battery is grounded by the closure of contacts 22,23. The contact 24 is normally closed on 40 the grounded contact 23 andenters into a test circuit to .be hereinafter described in detail.

The battery i0 is maintained under continuous charge by a rectifier 25having its positive terminal connected to the positive terminal of thebattery and its negative terminal normally connected for a low-rate ortrickle charge, but adapted under some circumstances to be connected fora high-rate charge. The charging connections are under the control of acharge control relay CC, the operation of which is disclosed in thecopending application. The relay CC has the contacts 26, 21, 28 and 29.The trickle charge is applied to the battery under normal conditionsthrough a resistance 30 con- V nected to the negative terminal or therectifier, a wire 32, contacts 28 and 29 of the relay CC, and a wire 34which leads to contact 2 of the test switch group B, and thence to thenegative battery terminal through the normally closed contacts 2, 3 ofgroup B and the wire I5. The

negative terminal of the rectifier is connected by g a lead 36 with thecontact 26, and the contact 21 is connected directly with terminal by alead 38. Upon energization of the charge control relay, the tricklecharge circuit is opened and the high-rate charge is applied.

The milliammeter I2 is connected between contacts I and 2 of group A,and is normally shunted when the group A is cammed as shown in Fig. 1.

The negative side 01' the line is connected to contact 2 01 group D andto contact 2 of group H by wires 46 and 48, respectively. The positiveside of the line is connected to contact 4 of group A, contact 2 ofgroup F, and contact 2 of group G by wires 50, 52 and 54, respectively.

The negative side of the battery is connected to contact 3 of group Dand the positive side of the battery is connected to contact 3 of groupC. To avoid confusion, the actual connections are not shown. but aremerely indicated by appropriate plus and minus signs.

Contact I 01 group C is connected to contact 2 of group E by a wire 56.Contact I of group D is connected to contact 3 of group F by a wire 58.Contact 3 of group A is connected to contact 2 01' group C by a wire 60.The voltmeter I3 is connected between contact I of group E and contact 4of group F. Contact I of group E is connected to contact I of group F bya wire 64. Contact 3 of group E, contact 5 of group F, contact I ofgroup G and contact I of group H are all connected to ground, butindirectly through a wire 66 leading to the contact 24 which is normallyclosed on contact 23 of the grounding relay MG, for purposes to be laterexplained. Contacts 3, 4 of both groups G and H are included in analternating current lamp circuit 68 shown in dash lines.

The seven follows:

I. Center positionnormal.

positions 01' the switch are as II. Line" positionto indicate linecurrent andvoltage.

111. Bat.".'positionto indicate battery charging current and voltage. IVand V. VGR" and "+VG to indicate voltage of either side 01' the linewith respect to ground.

VI and VII. "GR and +GR-to ground the positive or negative side of theline as a reference ground.

The connections for the several positions are described as follows:

I. Center or normal D s t -The switch groups are as shown in Fig. 1,group A only being cammed. The milliammeter contacts I, 2 of group A.All possible connections to the voltmeter are open. Accordingly noindication is given on either of the meters. This is the normalcondition.

11. "Line pOsitiOn.-In this position of the switch none of the groupsare cammed, switch groups A-and B being then as shown in Fig. 3.

Under these conditions the line current and the voltage across the lineare indicated on the meters.

15 The milliammeter shunt is broken at contacts 2 and the negativebattery 1 3 of group A. The line current, however, passes through themilliammeter by a circuit traced from the negative battery terminalthrough wire I5, contacts 3, 2 or B, wire I6, the milliammeter I2 andwire I6. The voltmeter circuit is traced as 5 follows: From the positiveline through wire 50, contacts 4, 3 of group A, wire 60, contacts 2, Iof group C, wire 56, contacts 2, I of group E, the voltmeter I3,contacts 4, 3 of group F, wire 58, contacts I, 2 of group D, and thelead 46 to the 10 negative side of the line.

III- "Bat? l osition.In this position of the switch groups B, C and Donly are cammed. Group A is not cammed and is, therefore, as shown inFig. 3, the milliammeter shunt being 15 open. Since group B is cammed,contact I is closed on 3 and the latteris moved away from 2. The tricklecnarge current is passed through the milliammeter by the followingcircuit: From the negative terminal of the rectifier through the goresistance 36, wire 32, contacts 23 and 29 of the charge control relayCC, wire 34, wire I6, the milliammeter I2 and wire I8 to contact I ofgroup B, where the current divides, one portion .going out on the lineand the other passing 25 through the now closed contacts I, 3 of group Band the wire I5 to the negative battery terminal. The trickle chargecurrent thus measured is the current supplied by the rectifier, which isthe sum of the line current and the battery current. It 30 is to benoted that if the charge control relay is .set for the high-rate charge,the charging current is not permitted to pass through the milliammeter,the wire 33 from the contact 21 leading direct to the negative batteryterminal. The 35 high-rate charge would exceed the range of themilliammeter.

The battery voltage is indicated on the voltmeter regardless of thecharging connections through the following circuit: From the positive 40terminal of the battery as indicated by the plus. sign under contact 3of group C, thence through contacts 3, I of the cammed group C, wire 56,contacts 2, I of group E, the voltmeter I3, contacts 4, 3 01' group F,wire 58, and contacts I, 3 45 of the cammed group D to the negativeterminal of the battery. P

IV. Voltage of negative side of line ab ve groumZ "VGR.In this positionof the switch contact groups A and E are cammed. The volt- 5 meterisconnected between the negative side of the line and ground through thefollowing circuit: From the negative side of the line through wire 46,contacts 2, I of group D, wire 58, contacts 3, 4 of group F, thevoltmeter I3, contacts 55 I, 3 of the cammed group E, wire 66, andcontacts 24, 23 of the relay MG to ground. Since group A is cammed themilliammeter is shunted.

. The purpose of this connection is to indicate whether or not a groundfault exists on the line. 50 If the line is in proper condition thevoltmeter should read zero. g

It will be notedthat if the grounding relay MG happens to be energizedwhen the switch is set on this position, the voltmeter circuit is 5broken at the open contacts 24, 23 of the relay MG. Since the negativeside of the battery is then grounded a reading of voltage above groundwould be meaningless. It is for this reason that contact 3 of group E isconnected indirectly to 70 ground through the wire 66.

V. Voltage 0 positive side of line above gr0und-+VGR. This position ofthe switch is similar to that previously described except that thevoltmeter is connected between the positive side of the line and ground.Groups A and F only are cammed. As for the other connection thevoltmeter should read zero if the line is in normal condition. Thevoltmeter circuit is traced from .the positive side of the line throughwire 52, contacts 2, l of the cammed group F, wire 64,

the voltmeter i3, contacts 4, of group F, wire 66, and contacts 24, 23of relay MG to ground.

If the relay MG is energized, this connection is ineffective.

VI and VII. Grounding of one side of the line.--To establish a referenceground as a preliminary for certain usual testing operations, either thepositive or negative side of the line may be grounded by moving theswitch to the points indicated +GR or -GR. To ground the positive sideof the line the switch groups A and G only are cammed and a circuit istraced from the positive side of the line through a. wire 54, contacts2, l of the cammed group G, wire 66 and contacts 24, 23 of the groundingrelay MG. For grounding the negative side of the line groups A and Honly are cammed so that the circuit is traced from the negative side ofthe line through wire 48, contacts 2, l of the cammed group H to thewire 68 from which the circuit continues to ground through the groundingrelay contacts. The fact that the circuit is completed through thegrounding relay permits establishment of the reference ground only whenthe line is in its normal closed loop condition. If the grounding relayhas been energized following a break in the line the negative side ofthe battery is grounded, and if a reference ground were then.established the battery and central ofilce equipment would beshort-circuited. The circuit through the grounding relay contactsprovided by the wire 66 prevents the short circuit in the event thegrounding relay is energized. The lamp circuit 68 is broken at contacts3, 4-of group G or contacts 3, l of group H whenever one side of theline is grounded.

The following general observation may be made concerning the functionsof the several switch groups: Group A is primarily a milliammeter shunt,although it also includes the contacts 3, 4 whereby the connection ofthe positive line to the voltmeter is controlled. Group'B is a selectorto cut the milliammeter circuit into either the negative line or thetrickle charge lead. Group C, D, E and F are voltmeter circuit controlswhereby a variety of connections to the voltmeter may be established,some complication of circuits arising from the necessity of isolatingboth sides of the meter from all points except those between which thevoltage is to be measured. Groups G and H are simply means forconnecting one side of the line to ground. I

The various switch connections above described provide for most of thenecessary testing operations on the line and in no way affect any normalcode signaling operation which may'occur while the switch is set in anyof its several positions. For example, although the normal position ofthe switch is in the center, the throwing of the'switch to either theline or bat." position merely throws the meters into circuit withoutopening the line. In the line position of the switch the milliammetershould read the normal line current and any deviation therefrom isindicative of some abnormal condition. The bat. position indicates thenormal trickle charge current unless the rectifier or its connectionsare 75 faulty or unless the charge control relay has for grounding oneside been set for the high-rate charge. The other four positions of theswitch do not involve any breaking into the line, but merely establishcertain connections with respect to ground. In

' any event, whether the line is normal or conditioned by the groundingrelay, no setting of the switch can interfere with a subsequentsignaling operation. This feature is important since in a system of thistype adapted for small town use and not under close personalsupervision, it may happen that the switch may be tampered with byunauthorized persons or may be inadvertently left in one of its testpositions after a test reading.

The invention having what is claimed is:

1. In a fire alarm system having a battery and a line, an ammeter,charging means for the battery, a trickle charge circuit and a high-ratecharge circuit, an ammeter switch for selectively cutting the ammeterinto the trickle charge circuit or the line, and. charge control meansfor connecting the battery with either charge circuit and havingprovision, for preventing connection of the ammeter into the high-ratecharge circuit.

2. In a fire alarm system having a battery and a line, an ammeter,charging means for the battery, a trickle charge circuit and a high-ratecharge circuit, and an ammeter switch for selectively cutting theammeter into the trickle charge circuit or the line, charge controlmeans for connecting the battery with either charge circuit and havingprovision for preventing connection of the ammeter into the high-ratecharge circuit, a voltmeter, and voltmeter switching means operable withthe ammeter switch for se-. lectively connecting the voltmeter to readthe battery voltage or the line voltage.

3. In a. fire alarm system having a line and a battery connectedthereto, a conditioning relay of the battery under abnormal conditions,and test switching means for establishing a circuit between one side ofthe line and ground, sad circuit including means controlled by theconditioning relay to prevent grounding of the line by said switchingmeans when the battery is grounded by said conditioning relay.

4. In aflre alarm system having a line and a battery connected thereto,a normally inactive conditioning relay having contacts to connect oneside of the battery to ground, a test switch to establish a circuitbetween one side of the line and ground, said circuit including contactsof the conditioning relay to prevent the ground connection when therelay is operative. y

5. In a fire alarm system having a line and a battery connected thereto,a test switch to ground one side of the line, a conditioning relayadapted under abnormal conditions to ground the battery, and meanscontrolled by the conditioning relay to prevent grounding of the line bythe test switch.

6. In a fire alarm system having a line and a battery connected thereto,test switching means for selectively grounding either side of the line,a conditioning relay operative under abnormal conditions to ground oneside of the battery and to connect both sides of the line together, andmeans controlled by the conditioning relay to render the test switchingmeans ineifective to ground the line.

been thus described,

FRANK R. BRIDGES. FOSTER E. WELD.

